The present invention is directed to what is often termed a free-falling, self-locking, adjustable tip assembly which has been previously described in U.S. Pat. Nos. 4,480,854 and 4,588,207. In these patents, the tip assembly is freely slidable on the belt so as to regularly adjust its position when the retractor rewinds the belt after its usage by a vehicle passenger. The usual manner of operation of such a tip assembly is that when the seat belt retractor begins to reel in the belt and the belt with the tip begins to move upwardly, the tip thereafter slides downwardly or does not move upwardly to a relatively high position with the upwardly traveling belt. On the other hand, the free sliding tip assembly is desired to be self-locking or snubbing across the passenger at a position across the lap of the passenger to prevent the shoulder portion of the seat belt from traveling through the tip assembly to a lower lap portion of the seat belt.
While the present invention may be usable in such a seat wherein the occupants are seated, as described in these patents, it is particularly directed to the situation of locking a baby seat in the rear seat of the vehicle. More specifically, it is desired to have a free-falling, self-locking, adjustable tip assembly in the rear seat which can be pulled across the baby seat and locked into a buckle at the rear seat. At the time of locking, it is desired that the lap portion of the belt which is across the baby seat be snubbed, or tightly held, so that the baby seat does not tilt or slide on the rear seat. Of course, when a person is seated on the rear seat, the locking tip will lock the lap portion of the belt at a fixed length so that a portion of the shoulder belt portion will not slide through the tip assembly to lengthen the lap belt. The shoulder belt is connected to the seat belt retractor at the upper end of the belt; and these retractors are usually inertia retractors that do not lock until the time that the inertia weight or means is operable, upon a sudden deceleration, to lock the retractor against further belt protraction from the retractor reel. The lap portion of the seat belt extends between an anchored end of the belt at the seat bench position and the buckle that is also fastened to the vehicle and positioned at the central portion of the rear seat bench. It is this fixed length lap portion between the buckle and the anchored belt end that should have a fixed locked length to hold the baby seat on the vehicle rear seat. Seat belt webbing from the upper shoulder belt should not be allowed to move through the tip assembly and into the lap belt portion and thereby allow the baby seat to shift its position. The desired locking or gripping for the tip assembly is in the range of 1,200 to 1,600 pounds of force on the belt.
Present specifications require the holding of the belt by the tip assembly to be at least 1,200 pounds and with a safety factor, to be 1,600 pounds. One of the particular problems of finding such a high-locking force is the criteria that the tip must be free-falling. Also, a further requirement is that the locking at such a high force will be not a one-time situation in which the tip is so wedged or otherwise connected so that it cannot be slid down the belt after a high force locking of 1,200 to 1,600 pounds.
In addition, it is desirable that the particular locking structure be such that it does not readily abrade the belt and meets abrasion cycle tests which are necessary for commonly-used seat belts that are used over and over again.
The construction shown in U.S. Pat. No. 4,480,854 has worked well for the use in the front seats and other seats where it is used; and it cannot be used in its present state for the rear seat usage to hold a baby seat because, in tests, it is found that it only holds up to 300 pounds before the belt slips through the snubbing means. On other hand, U.S. Pat. No. 4,588,207 is designated to slip at a very light load, for example, a 50 pound load.
While other devices have been tried, a number of them had the ability to hold the web against slipping at high loads, but they cannot be disconnected because the pieces were so jammed together after a 1,200 to 1,600 pound load that the tip would no longer slide on the belt. Such a tip would have but only a single use and would have to be replaced or tools would have to be used to try to separate the snubbed parts. On the other hand, the present invention provides a structure which will readily separate and be free-falling after a locking force in excess of the 1,200 to 1,600 pound range, and, in fact, the present invention has been successfully operated to grip with loads of 2,100 pounds and still release and be free-falling on the belt.